1. Field of the Invention
The present invention relates to a safety ski binding comprising front and rear retention elements for retaining the boot on the ski. The front element is generally called a front abutment or toe binding and the rear element is generally called a heel binding.
2. Description of Background Information
The front abutment of a safety ski binding is adapted to laterally pivot against the bias of an elastic mechanism which can be adjusted to a predetermined value. As a result, when excessive torsional forces act on the leg of the skier which are greater than the predetermined value, the boot and the front abutment pivot in the lateral direction, thereby freeing the boot of the skier from the front abutment.
Conventional safety bindings that use this laterally pivotable front abutment suffer a number of disadvantages, particularly when a torsional fall which causes the boot of the skier to laterally pivot, is combined with a frontward fall. In this case, the bottom of the front of the sole of the boot is pressed downwardly against the ski with a substantial force. This downward force of the front of the sole of the boot on the ski creates friction between the bottom of the sole and a support surface of the ski. This frictional force is appreciable and opposes lateral release of the boot, which is dangerous to the skier.
Various bindings have been designed to compensate for this frictional resistance to lateral release of the boot. For example, German Pat. No. 29 05 837 places a sensor under the front of the sole of the boot to act on the latching mechanism of the binding. This sensor comprises a pedal which is actuated when the front of the boot presses downwardly on the pedal during a frontward fall. The pedal compensates for the friction of the sole of the boot on the ski by reducing the release threshold of the front abutment above which lateral release of the boot occurs. This release threshold is reduced by an amount equal to the value of the friction generated by the sole of the boot against the ski.
Another binding which attempts to solve this problem is French Pat. No. 2,523,857. In this patent, the compensation mechanism described in French Pat. No. 2,314,742 of June 20, 1975 is used. French Pat. No. 2,314,742 described a front abutment in which the elastic system comprises a spring supported against two tiltable elements journalled relative to one another. During a rearward fall the lifting of the front of the boot causes the rotation of one of the tiltable elements with respect to the other, thereby dividing the bias of the spring into two components. This dividing of the bias of the spring into two components diminishes the bias against lateral pivoting so as to compensate for the friction between the boot and the ski.
In French Pat. No. 2,523,857, the rearward fall compensation mechanism of U.S. Pat. No. 2,314,742 is used to compensate for friction between the boot and the ski during a forward fall. This is accomplished by attaching a mobile element of the abutment to a plate which exerts an upward pressure on the bottom of the mobile element, thereby causing a torque on the mobile element which pivots the mobile element upwardly in the case of a rearward fall. As a result, a compensation effect is automatically obtained by diminishing the elastic bias of the movable element retaining the front of the boot against lateral pivoting.
French Certificate of Addition Application No. 8319397 of Dec. 5, 1983 provides a different solution to the problem of friction between the boot and the ski. In this application, a pivotable plate is provided which exerts, in the event of a frontward fall, a rearward of traction force on the front abutment. As described in this Certificate of Addition and as described in the principle patent, French Pat. No. 8310819, which are hereby incorporated by reference, the abutment is of a type which pivots around one of two pivot axes positioned symmetrically on both sides of the plane of symmetry of the abutment. This tractional force causes a torque to be applied to the abutment which causes an additional rotation of the abutment to compensate for the friction of the boot against the ski which tends to limit such rotation.
In these two types of bindings, a pivotable plate is used which slides in the longitudinal direction of the binding. The plate is adapted to support a rear heel binding so that the force of lifting the heel of the boot causes a rearward movement of the plate. Because the plate is attached to the front abutment, this rearward movement of the plate transmits a tractional force to the abutment in the rearward direction. However, in these two types of bindings, the pivotable plate and the front abutment are attached to one another by a simple pivot. As a result, if the pivot is positioned so that the longitudinal axis of the boot coincides with the longitudinal axis of the plate during lateral pivoting, this pivot is positioned a substantial distance from the pivot axis of the front abutment, which is disadvantageous because the pivot at which the traction force of the plate is applied to the abutment is not as close as possible to the rotation axis of the abutment. If the position of the pivot is moved closer to the pivot axis of the front abutment, the longitudinal axis of the boot will not coincide with the longitudinal axis of the plate during lateral pivoting, which is also disadvantageous. Therefore, there is a need for a linking mechanism between the plate and the front abutment that permits that portion of the plate which transmits the traction force to the front abutment to be as close as possible to the rotation axis of the front abutment, will at the same time permit the longitudinal axis of the boot to coincide with the longitudinal axis of the plate during lateral pivoting.